Optical properties of "IntralipidTM", an aqueous suspension of lipid droplets.

by Steven Jacques, Oregon Medical Laser Center, 1 April 1998

IntralipidTM (Kabivitrum Inc., California and Stockholm) is a brandname for an aqueous suspension of lipid droplets that is sterile and suitable for intravenous feeding of patients. There are other brands (NutralipidTM (Pharmicia, Quebec), LiposynTM (Abbot Labs, Montreal)) which should be similar in composition. Available as Intralipid-10% and Intralipid-20% (10% lipid indicates 10 g of lipid per 100 ml of suspension). The constituents of Intralipid-10% in a 500 mL bottle according to the manufacturer are:

soybean oil

50 g

53.94 mL

lecithin

6 g

5.82 mL

glycerin

11.25 g

8.92 mL

water

430.5 g

431.33 mL

TOTAL

497.75 g

500 mL

There is sufficient bottle-to-bottle variation in the optical properties of commercially available Intralipid, or other brandname products, that optical properties should be verified experimentally for each bottle at the time of use. Therefore, the properties reported here are simply approximate.

Uses of Intralipid

Used for intravenous feeding of patients. Used in the biomedical optics community as a scattering medium for phantoms that mimic turbid tissues when conducting optical experiments.

Optical property data

The optical properties of a Intralipid-10% is shown in the following figures. The optical properties shown in the figures are:

absorption coefficient, mua [cm-1]

reduced scattering coefficient, mus' = mus*(1-g) [cm-1]

scattering coefficient, mus [cm-1]

anisotropy of scattering, g [dimensionless]

The determination of optical properties by Flock et al. and in our HeNe laser experiment were based on diffuse reflectance measurements on Intralipid-10% with and without added absorber. Total attenuation of collimated light was measured. Click here for experimental procedures.

The determination of optical properties by van Staveren et al. was based on experimental measurements of light diffusion within Intralipid-10% with and without added absorber. Total attenuation of collimated light was measured. In addition, Mie theory calculations of anisotropy, g, based on lipid droplet size distributions determined by experimental freeze fracture and electron microscopy, were shown to closely agree with the experiments. This summary cites their simple expressions which approximate the Mie theory solutions. Click here for experimental procedures.

The absorption coefficient of Intralipid-10%.

For comparison, 10% of the absorption of pure soybean oil is shown, and 90% of the absorption of pure water is shown. (The water data of Hale and Querry, Applied Optics 12:555-563, 1973, was multiplied by 0.90.) The error bars (standard deviations) of the intralipid are quite large, but the results show that the approximate absorption of 10% Intralipid is probably well approximated by the combination of 10% soybean oil and 90% water.
Blue solid circle is our recent HeNe laser experiment.Click here to enlarge

The reduced scattering coefficient of Intralipid-10%.

In summary, the optical properties of Intralipid-10% are summarized. The variations between the data of Flock, van Staveren, and our recent HeNe experiment may indicate the variation in the batches of Intralipid used. Other data from various investigators cited in Flock et al. (Table 1 and Fig. 7 of that paper) show a range of values for mus and g that vary between the Flock and van Staveren data summarized here. One should document the optical properties of the batch of Intralipid to be used in an experiment, and one should be confident of the measurement techniques used for such documentation.